Everybody is making a big deal about the battery changes, but you're right: the really important part of this announcement is profitability. This is HUGE for Tesla, as it proves their model is successful.
Though it won't be the least efficient, it'll be right down there. (Subsidizing and "protecting" steelmakers and automakers in the past pretty much doomed those industries to stop being innovative or competitive on the world market.)
If you are looking for a very rough approximation of what a gasoline car needs to cost, scroll down to where someone explains the pricing in Norway.
Where did you get that last claim from? You seem to be missing all the caveats that would be necessary to make it true. Did you perhaps really mean to say something like: there hasn't been a single successful new company (for some definition of "success") in the last X years that survived until today without getting bought by a larger firm? Because the thing you actually did say isn't true.
Unless you can come up with a way to argue that, say, The DeLorean Motor Company wasn't a "new car company" founded in the last "over 100 years". And do the same for a dozen others of less renown (eg, the Muntz Car Company)
I know you're exaggerating for effect, but when has such a scheme ever worked to bring a new technology mainstream? The government didn't need to give you a tax credit to buy a PC.
I suspect it would be much more efficient to slowly, predictably ramp up gasoline or carbon taxes, offset with, say, lower payroll taxes. Effectively no cost to the government, and it lets the market decide how best to reduce emissions.
Maybe, but you are comparing "it would be better to do this optimal thing which hasn't actually happened and may be politically hard to make happen" to "this thing that actually did happen was worthwhile". Both can be true.
The government didn't need to give tax credits for PCs because they directly funded much of that research via research grants and there were more immediate uses for PCs in the corporate and military world. Corporations aren't about to buy fleets of electric cars.